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Date: Thu, 18 Jun 2015 10:48:34 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Denys Vlasenko <vda.linux@googlemail.com>,
        Borislav Petkov <bp@alien8.de>, X86 ML <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: For your amusement: slightly faster syscalls
Message-ID: <20150618084834.GA16323@gmail.com>
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* Ingo Molnar <mingo@kernel.org> wrote:

> 
> * Andy Lutomirski <luto@amacapital.net> wrote:
> 
> > On Mon, Jun 15, 2015 at 2:42 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> > > On 06/15/2015 02:30 PM, Linus Torvalds wrote:
> > >>
> > >> On Jun 12, 2015 2:09 PM, "Andy Lutomirski" <luto@amacapital.net
> > >> <mailto:luto@amacapital.net>> wrote:
> > >>>
> > >>> Caveat emptor: it also disables SMP.
> > >>
> > >> OK, I don't think it's interesting in that form.
> > >>
> > >> For small cpu counts, I guess we could have per-cpu syscall entry points 
> > >> (unless the syscall entry msr is shared across hyperthreading? Some msr's are 
> > >> per thread, others per core, AFAIK), and it could actually work that way.
> > >>
> > >> But I'm not sure the three cycles is worth the worry and the complexity.
> > >
> > > We discussed the per-cpu syscall entry point, and the issue at hand is that it 
> > > is very hard to do that without with fairly high probability touch another 
> > > cache line and quite possibly another page (and hence a TLB entry.)
> 
> ( So apparently I wasn't Cc:ed, or gmail ate the mail - so I can only guess from 
>   the surrounding discussion what this patch does, as my lkml folder is still 
>   doing a long refresh ... )

Hm, it's nowhere to be found. Could someone please forward me the original email?

Thanks,

	Ingo